IS Loughlin — Relations between the Quincy Granite 



The question thus arises : what are the exact age and struc- 

 tural relations between the Quincy granite and the adjacent 

 sedimentary formations? An answer, based on petrographic 

 and structural evidence, and on the finding of Quincy granite- 

 porphyry pebbles in the Norfolk Basin only, is given in the 

 following pages. The evidence appears to prove that the 

 Quincy granite is older than both sedimentary formations, and 

 in the main, to confirm Prof. Crosby's conclusions; but.it 

 raises other cpiestions of structural and stratigraphic geology, 

 which will be cited at the close of this paper. 



Fig. 1. 



Fig-. 1. Outline map showing positions and areas of the three sedimentary 

 basins in S.E. New England (mostly after W. O. Crosby and J. B. Wood- 

 worth). " Q " represents the Quincy granite series. 



Outline of Geology. 



The area involved in the present discussion is shown on the 

 map (fig. 2). The oldest rocks of the district are Cambrian 

 slates, of considerable extent in the eastern part of the area 

 but elsewhere represented only by scattered patches. They 



